1. Field of the Invention
The present invention relates to an electrophotographic image forming apparatus for forming an image on a recording medium in the state that a process cartridge having an electrophotographic photosensitive drum and a process device for acting on the electrophotographic photosensitive drum is detachably mounted to a main body of the image forming apparatus.
Here, the electrophotographic image forming apparatus (hereinafter referred to as ‘image forming apparatus’) forms an image on a recording medium using an electrophotographic image forming process. The examples of the image forming apparatus include an electrophotographic copying machine, an electrophotographic printer (for example, an LED printer), a facsimile device, and a word processor. As an image forming apparatus, both monochrome image forming apparatuses and color image forming apparatuses are included. The recording medium is a material on which an image is formed by the image forming apparatus, and includes a paper sheet and an OHP sheet. An intermediate transfer member is also included.
In general, the cartridge is, for example, a process cartridge or a developing cartridge which is detachably mounted to the main body of the electrophotographic image forming apparatus to contribute to an image formation process for forming an image on the recording medium. The process cartridge integrates at least one of a charge member, a developing member and a cleaning member as a process device for acting on a drum and the drum into a cartridge and detachably mounts it to the main body of the apparatus. Therefore, the cartridge includes the type of cartridge integrating the developing member as a process device and the drum into a cartridge and detachably mounting it to the main body of the apparatus. The process cartridge also includes the type of cartridge integrating the charge member, the developing member or the cleaning member as a process device and the drum into a cartridge and detachably mounting it to the main body of the apparatus. The type of process cartridge that integrates the drum and the developing member is called an ‘integral type’. The type of process cartridge that integrates the drum and the process devices other than the developing member is called a ‘discrete type’. The process cartridge can be mounted to and demounted from the main body of the apparatus by a user. For that reason, the maintenance of the main body of the apparatus is easy. In addition, the developing cartridge has a developing roller, accommodates a toner, and is detachably mounted to the main body of the apparatus, wherein the toner is used by the toner roller to develop an electrostatic latent image formed on the drum. In the case of the developing cartridge, the drum is mounted to the main body of the apparatus or a cartridge supporting member. Or, the drum is provided in the discrete type process cartridge (in this case, the process cartridge does not have the developing member). The developing cartridge can also be mounted to and demounted from the main body of the image forming apparatus by the user. For that reason, the maintenance of the main body of the apparatus is easy. As for the cartridge, the integral type process cartridge and the discrete type process cartridge are included. The discrete type process cartridge and the developing cartridge may be paired and used as a cartridge. The drum is fixed to the main body of the apparatus or a cartridge supporting member, and the developing cartridge is detachably mounted to the cartridge supporting member to be actable on the drum. In the present invention, the cartridge, having the electrophotographic photosensitive drum (hereinafter referred to as ‘drum’) and the process device for acting on the drum, is detachably mounted to the main body of the apparatus for use.
2. Description of the Related Art
In order to downsize the image forming apparatus, a light emitting device may be used as an exposure device for the drum, wherein the light emitting device has light emitting elements arrayed in the longitudinal direction (in the direction of the shaft) of the drum for emitting in accordance with image information to expose the drum. For example, in the image forming apparatus using LEDs as the light source of the exposure device, a condenser lens for condensing light emitted from the LEDs onto the drum is provided. Japanese Patent Application Laid-Open No. 2002-91268 describes the image forming apparatus having LEDs as the light source of the exposure device provided for the process cartridge that integrates the drum, the developing member and the like, and also having a condenser lens provided for the main body of the apparatus.